The present invention is directed to a treatment facility, particularly for printed circuit boards to be treated in a horizontal passage through the facility. The treatment facility includes a treatment cell to which a treatment fluid can be supplied from a supply reservoir by means of a pump, and has a drain line for discharging the supply treatment fluids emerging from the treatment cell back to the supply reservoir.
Treatment facilities, which have a continuous circulation of the treatment fluid, are particularly utilized in electroplating technology for pre-treatment, metallization and after-treatment of the workpieces. Utilization in currentless metallizations of a workpiece is likewise possible. Dependent on the nature of the treatment fluid utilized, air can be worked into the treatment fluid during the out-flow from the treatment facility into the supply reservoir and foam can be formed in the supply reservoir. Particularly given treatment fluids having a high wetting agent content, such as, for example, in a cleaner/conditioner solution employed for preparation of currentless metal deposition or given electrolyte solutions for the electro-deposition of tin, such a pronounced formation of foam can occur that great quantities of foam will emerge from the supply reservoir into the treatment facility.
When printed circuit boards are to be treated by a horizontal passage through a machine or treatment cell, an intense flooding of the through contact holes of the printed circuit board on the basis of particularly intensive circulation of the respective treatment fluid is achieved. However, the undesirable foaming will be promoted with increased circulation.
Anti-frothing agents are substances added to the foaming fluids in order to reduce or prevent foam formation. The anti-frothing agents are either surface-active substances which displace the frothing agent from the interface surface without themselves being frothing agents or, on the other hand, are products which increase the surface tension of the fluid. However, given the described treatments facility, the addition of such anti-frothing agents would have a considerable negative effect on the properties of the respective treatment solutions. Thus, chemical agents are excluded as a means for combatting the formation of foam.